1. Field of the Invention
The invention relates to a steam trap. More particularly it relates to a steam trap of the type having a bimetallic control element arranged on the preliminary pressure side of the trap and a closure member actuated by the bimetallic control member which is biased in the opening direction by the preliminary pressure and which cooperates with a valve seat.
2. The Prior Art
A known steam trap of this type (DE-AS 1 183 098) comprises a control element with a plurality of circular bimetallic plates. Radial slots in the bimetallic plates form active arms whose ends support the bimetallic plates. The bimetallic plates have identical dimensions apart from the slot lengths, i.e. a bimetallic plate with longer slots and a bimetallic plate with shorter slots and therefore shorter active arms are provided. The active arms of a bimetallic plate are all of equal length in each case. Owing to the different bimetallic plates, the control element has a closing force line which is adapted to the saturated steam curve of the condensate to be drained. A significant drawback of this known steam trap resides in the need for different bimetallic plates.
With another known steam trap (DE AS 1 261 127, DE GM 1 917 348) the active arms of the bimetallic plates have different lengths. Each bimetallic plate therefore has a closing force line adapted to the saturated steam curve. However, these bimetallic plates are very large and protrude outwardly. Therefore, this steam trap requires a large housing.